Investigating the electrical and optical characteristics of lead-free all-inorganic Cs3Sb2Br9 single crystals

Abstract

In recent years, halide perovskites have emerged as promising materials for electronic devices. While lead-based perovskites have been extensively studied, exploration of lead-free variants has been limited. Here, we highlight the innovation of observing negative photoconductivity (NPC) induced by light, followed by self-recovery, in lead-free Cs3Sb2Br9 perovskite single crystals. Our study reveals the self-trapping of holes at the Vk center, corresponding to the Br2− dimer, within the midband states of this vacancy-ordered perovskite. This leads to the entrapment of photogenerated charge carriers by charged defect states denoted as Vk, creating an internal electrical field that counteracts the externally imposed field, resulting in NPC. We demonstrate the innovation through the construction of a prototype photodetector with notable sensitivity, featuring high responsivity (6.77 mA/W), detectivity (2.83 × 1012 Jones), and a dark-to-light current ratio of approximately 10. This recognition of retroactive photocurrent in optically active perovskite materials holds promise for advancing highly sensitive detectors.